Plasma device

ABSTRACT

A plasma apparatus includes a patch antenna emitting a high frequency wave into a processing container. The patch antenna has a conductive plate forming a resonator and a ground plane. The conductive plate of the patch antenna is fed such that the emitted high frequency wave becomes a circular polarization.

TECHNICAL FIELD

The present invention relates to a plasma apparatus generating plasma bya high frequency wave or an electromagnetic field to perform prescribedprocesses.

BACKGROUND ART

Plasma apparatuses are widely used in manufacturing semiconductordevices, to perform processes such as oxide film formation, crystalgrowth of a semiconductor layer, etching and ashing. Among such plasmaapparatuses, there is a high frequency plasma apparatus that supplies ahigh frequency wave into a processing container using an antenna, andgenerates high-density plasma. The high frequency plasma apparatus iscapable of generating plasma stably even when plasma gas pressure isrelatively low, and hence, application thereof is wide.

Recently, the use of a patch antenna in this high frequency plasmaapparatus has been studied as an antenna for supplying a high frequencywave into the processing container. FIGS. 37A-37C shows an exemplaryconfiguration of a conventional patch antenna used in the high frequencyplasma apparatus. FIG. 37A is a plan view of the patch antenna viewedfrom the emitting surface, FIG. 37B is a cross section along a lineXXXVIIB-XXXVIIB of FIG. 37A, and FIG. 37C shows coordinate systemscorresponding to FIG. 37A.

As shown in FIG. 37B, the patch antenna has a ground plane 531 formed ofa grounded conductive plate, and a conductive plate 532 forming aresonator. Ground plane 531 and conductive plate 532 are provided atopposing faces of a dielectric plate 534, respectively. Conductive plate532 is connected at its center O to ground plane 531 by a conductiveline 533 that penetrates dielectric plate 534.

As shown in FIG. 37A, the two-dimensional shape of conductive plate 532is a rectangle, in which the length of the longer edge is L1 and that ofthe shorter edge is L2 (L2<L1). When the wavelength of theelectromagnetic field in the patch antenna is given as λg, the length ofthe longer edge L1 is set to L1≈λg/2. For ease of description, x axisand y axis are assumed to be parallel to the longer edge and the shorteredge of conductive plate 532, respectively, and the origin of thecoordinate systems is assumed to be at center O of conductive plate 532.

As shown in FIG. 37B, the patch antenna is connected to a high frequencypower source 545 through a coaxial line 541. Here, an outer conductor542 of coaxial line 541 is connected to ground plane 531, while an innerconductor 543 of coaxial line 541 penetrates an opening of ground plane542 and dielectric plate 534 to be connected to conductive plate 532 ata point PP on x axis.

FIGS. 38A and 38B are for describing the principle of radiation of theelectromagnetic field by the patch antenna. Here, FIG. 38 A showsconductive plate 532, while FIG. 38B shows a current distribution(dotted line) and a voltage distribution (solid line) in x axisdirection in conductive plate 532.

As the length of the longer edge L1 is approximately λg/2, the currentsupplied from high frequency power supply 545 to conductive plate 532resonates in the longer edge direction, i.e., in the x axis direction,to be a standing wave, of which current distribution takes the form ofsine wave where the opposing ends are fixed to 0 (zero), as indicated bythe dotted line in FIG. 38B. When the current resonates and becomes sucha standing wave, the waveform of the voltage and the waveform of thecurrent have different phases from each other by 90°.

In the state shown in FIG. 38B, the voltage at the left end ofconductive plate 532 is positive, and therefore the line of electricforce is directed from conductive plate 532 to ground plane 531. On theother hand, the voltage at the right end of conductive plate 532 isnegative, and therefore the line of electric force is directed fromground plane 531 to conductive plate 532. As the direction of the lineof electric force is the same as a displacement current, magneticcurrents flow in the same direction along the left and right ends ofconductive plate 532, as shown in FIG. 38A. As an electromagnetic fieldis emitted having the magnetic currents as the wave source, theelectromagnetic field forms a TM10 mode in which the magnetic field isparallel to y axis.

FIGS. 39A and 39B are conceptual illustrations of field intensitydistributions formed by the patch antenna. FIG. 39A indicates the fieldintensity distribution in the xz plane, while FIG. 39B indicates thefield intensity distribution in the yz plane.

As above, as the electromagnetic field emitted by the patch antennaforms the TM10 mode in which the magnetic field is parallel to y axis,the field intensity distributions thereof show characteristics similarto a dipole antenna, as shown in FIGS. 39A and 39B. Specifically, whileit is relatively uniform in the xz plane as in FIG. 39A, large biasoccurs in yz plane as in FIG. 39B. The field intensity distribution inthe yz plane shows the greatest electric field at center O of conductiveplate 532, and electric field is weakened noticeably as distancedtherefrom.

Accordingly, when plasma is generated in an electromagnetic field withsuch a spatial distribution, the field intensity being higher on x axisthan the surroundings results in the plasma density directly under xaxis being higher than the surroundings. Accordingly, there has been aproblem that when an etching apparatus is formed with a conventionalplasma processing apparatus using a single patch antenna of whichoperation is similar to a dipole, the processing speed thereof variesdepending on the location, i.e., the etching speed becomes faster in thearea immediately under x axis where the plasma density is high. This isthe first problem.

Recently, the processing container tends to have a larger diameter asthe size of a wafer or an LCD (liquid crystal display) increases. As thediameter of the processing container increases from the sizecorresponding to a half wavelength (λg/2) of the high frequency waveused to the size corresponding to one wavelength (λg), and furtherincreases more than the size corresponding to one wavelength, a standingwave is generated in the processing container in the radial direction orthe peripheral direction. The electric field is great at the antinode ofthe standing wave, while it is small at the node thereof, therefore thestanding wave generated in the processing container hinders control ofplasma to be uniform. Accordingly, when making the diameter of theprocessing container larger, it is necessary to set the wavelength ofhigh frequency wave used longer correspondingly so that the standingwave would not be generated.

For avoiding the generation of the standing wave in the processingcontainer, there is a conventional example to use a dipole antenna as anantenna for supplying the electromagnetic field of high frequency intothe processing container. FIG. 40 shows a plan view of the dipoleantenna.

The dipole antenna 3530 is arranged on a dielectric plate 3512 thatisolates the antenna from a processing container (not shown) generatingplasma, and formed with two conductive poles 3531, 3532 arrangedlinearly and parallel to the main surface of dielectric plate 3512. Theopposing ends of conductive poles 3531, 3532 are away from each other,and connected to a high frequency power source 545 for feedingelectricity. In order to emit an intense high frequency wave using aresonance phenomenon, dipole antenna 3530 needs to have a length of anodd multiple of a half wavelength (i.e., (2N−1)×λg/2, where λg is thewavelength of the electromagnetic field above dipole antenna 3530 and Nis a natural number).

Dipole antenna 3530 can only be used with the processing containerhaving a diameter L approximately larger than λg/2 due to its antennasize of (2N−1)×λg/2. Conversely, if dipole antenna 3530 is employed,with the processing container with diameter L, the high frequency wavehaving a wavelength approximately higher than 2 L can not be used (inother words, the high frequency wave having a wavelength approximatelylower than c/(2 L) (where c is the speed of light) can not be used). Asabove, there has been a problem that the use of dipole antenna 3530 inthe plasma apparatus limits the diameter of a suitable processingcontainer, or the frequency of the high frequency wave. This is thesecond problem.

FIG. 41 shows an exemplary configuration of an etching apparatus using aconventional high frequency plasma apparatus. FIGS. 42A and 42B show theconfiguration of a patch antenna used in the etching apparatus. Here,FIG. 42A is a plan view of patch antenna 4530 shown in FIG. 41 viewedfrom the bottom, while FIG. 42B shows coordinate systems.

In the etching apparatus shown in FIG. 41, a sealed container is formedby a cylindrical processing container 511 open at the upper portion, anda dielectric plate 512 closing the upper opening of processing container511. At the bottom of processing container 511, an exhaust port 515 isprovided for vacuum evacuation. On a sidewall of processing container511, a processing gas supply nozzle 517 is provided for introducingetching gas. In processing container 511, a mounting table 522 isaccommodated for placing a substrate 521 to be etched. To mounting table522, a high frequency power source 526 for bias is connected.

To the upper portion of dielectric plate 512, a patch antenna 4530 isarranged for supplying a high frequency electromagnetic field intoprocessing container 511 through dielectric plate 512. Shield member 518covers the periphery of dielectric plate 512 and antenna 4530. Antenna4530 is connected to high frequency power source 545 for feedingelectricity.

Patch antenna 4530 has a ground plane 4531 formed with a groundedconductive plate, and a conductive plate 4532 arranged facing to groundplane 4531 to form a resonator (hereinafter referred to as a patch). Asshown in FIG. 42A, patch 4532 is in a circular shape (two-dimensionally)having a diameter L1≈λg. λg is a wavelength of the electromagnetic fieldbetween patch 4532 and ground plane 4531. Here, it is assumed that patch4532 is on the xy plane of which center O is the origin of thecoordinate systems.

As shown in FIG. 41, in patch antenna 4530, a feed point is provided atcenter O of patch 4532. Coaxial line 541 is used for feeding antenna4530, of which outer conductor 542 is connected to ground plane 4531,while inner conductor 543 is connected to center O of patch 4532.

Additionally, patch 4532 is connected to ground plane 4531 through shortpins 4533 at three points P1, P2, P3, which are isotropically away fromcenter O by approximately λg/4. It is assumed that point P1 is on xaxis.

FIGS. 43A and 43B shows the operating principle of patch antenna 4530.Diameter L1 of patch 4532 is approximately λg, and therefore the currentsupplied from high frequency power source 545 to center O of patch 4532oscillates to be a standing wave. As shown in FIG. 43B, the voltagewaveform at this time on x axis becomes an antinode at center O, whichis the feeding point, and becomes a node at point P1 that is grounded.At the periphery of patch 4532 the voltage changes at the same phase,therefore as shown in FIG. 43A, magnetic currents generated along theperiphery of patch 4532 take the same direction along the entireperiphery as viewed from center O. Accordingly, with patch antenna 4530,the TM01 mode is excited, but not the TM11 mode.

Patch antenna 4530 emits a high frequency wave with the above describedmagnetic currents as the wave source. The electromagnetic field of thishigh-frequency wave supplied into processing container 511 throughdielectric plate 512 causes electrolytic dissociation of a gas inprocessing container 511, to generate plasma in an upper space 550 abovesubstrate 521 to be processed. The plasma diffuses in processingcontainer 511, and the energy, anisotropy or the like thereof iscontrolled by the bias voltage applied to mounting table 522 to be usedin the etching process.

However, when patch antenna 4530 is in the TM01 mode, the directivity ofthe high frequency electromagnetic field will be, as shown in FIG. 41,horizontal that is parallel to the main surface of patch 4532 (i.e., thexy plane). Accordingly, a large amount of electricity will be convertedto thermal energy at shield member 518 or at processing container 511before contributing to the generation of plasma. Therefore, there hasbeen a problem that plasma can not be generated effectively. This is thethird problem.

DISCLOSURE OF THE INVENTION

First and second inventions are made to solve the first problem.Specifically, the object thereof is to enable a uniform plasmaprocessing as compared to the conventional manner.

A third invention is made to solve the second problem. Specifically, theobject thereof is to increase the degree of freedom in designing aplasma apparatus that has been limited by the size of the antenna.

A fourth invention is made to solve the third problem. Specifically, theobject thereof is to increase the efficiency of power at plasmageneration.

To provide a plasma apparatus that can perform plasma processing ofhigher quality by solving these first to third problems is the commonobject of the first to fourth inventions.

In order to achieve the objects above, a plasma apparatus according tothe first invention is characterized by an antenna emitting a highfrequency wave into a processing container having a conductive platearranged facing to a mounting table arranged in the processing containerto form a resonator, and a ground plane arranged facing to theconductive plate at a side opposite to the mounting table. Theconductive plate is fed such that the emitted high frequency wavebecomes a circular polarization. By making the high frequency waveemitted from the antenna to be a circular polarization, the spatialdistribution of an electromagnetic field inside the processing containerbecomes uniform as compared to the conventional manner. The highfrequency emitted from the antenna may not be a perfectly circularpolarization, and it may be a circular polarization with a polarizationratio of at least 50%, preferably 70%.

Here, two feeding lines may be used for feeding the conductive plate.Specifically, the circular polarization may be generated by two-pointfeeding.

In this case, the two feeding lines may feed such that that two linearpolarizations equal in amplitude, having different phases from eachother by 90°, and spatially perpendicular to each other are emitted,respectively. Thus, the high frequency wave emitted from the antennabecomes a circular polarization, which results in even uniform spatialdistribution of the electromagnetic field in the processing container.

Further, when the conductive plate has a 90° rotational symmetric form,the two feeding lines may be connected to the conductive plate at twopoints thereon away from a center of the conductive plate bysubstantially equal distances and in two directions perpendicular toeach other as viewed from the center, for feeding in equal amplitude andwith phases different from each other by 90°, respectively.

Still further, in the plasma apparatus described above, one feeding linemay be used for feeding the conductive plate of the antenna.Specifically, the circular polarization may be generated by one-pointfeeding. In this case, the two-dimensional shape of the conductive platemay be a shape having two different lengths in two directionsperpendicular to each other as viewed from the center thereof. Thefeeding line may be connected to the conductive plate at one pointthereon in a direction between the two directions. In this case, theconductive plate may have a two-dimensional shape of a circle of whichperipheral region is cut out, or an ellipse or a quadrangle.

In order to achieve such an object, a plasma processing apparatusaccording to the present invention is characterized by an antennaarranged facing to a mounting surface of a mounting table arranged in aprocessing apparatus for supplying an electromagnetic field of a highfrequency wave into the processing container is formed of a plurality ofmonopole antennas, and configured such that the electromagnetic fieldforms a circular polarization. Thus, by rotating the electromagneticfield around the axis perpendicular to the mounting surface of mountingtable, the plasma distribution generated by the electromagnetic fieldrotates as well. Thus, the uniformity of plasma distribution whenaveraged by time can be improved.

Here, the electromagnetic field emitted from the antenna may not be aperfectly circular polarization, and it may be a circular polarizationwith a polarization ratio of at least 50%, preferably 70%.

Further, a plasma processing apparatus according to the presentinvention is characterized by an antenna arranged facing to a mountingsurface of a mounting table arranged in a processing apparatus forsupplying an electromagnetic field of a high frequency wave into theprocessing container is formed of a plurality of monopole antennas, andconfigured such that the electromagnetic field forms a substantial TM01mode. Since the electric field in the substantial TM01 mode isdistributed approximately radially around an axis perpendicular to themounting surface of the mounting table, the uniformity of the plasmadistribution in a plane parallel to the mounting surface can beimproved.

It is preferable to use a patch antenna for the monopole antenna. Byusing the patch antenna, the magnetic current forming portion can bemade longer to improve the radiation efficiency of the electromagneticfield.

The patch antenna includes a conductive plate arranged facing to themounting surface of the mounting table, a ground plane arranged facingto the conductive plate at a side opposite to the mounting table asviewed from the conductive plate, a conductive member connecting one endof the conductive plate to the ground plane, and a feeding lineconnected to the conductive plate at a point away from the one end ofthe conductive plate. The one end of said conductive plate of said patchantenna, which is connected to the ground plane through the conductivemember, may be substantially straight, and a length in a directionperpendicular to the one end may be at most approximately ¼ of awavelength of the electromagnetic field in the patch antenna.

Alternatively, the patch antenna includes a conductive plate arrangedfacing to the mounting surface of the mounting table and havingsubstantially straight one end and arc-shaped other end opposing to theone end, a length between the one end and the other end being at most(1.17±0.05)/4 of a wavelength of the electromagnetic field in the patchantenna; a ground plane arranged facing to the conductive plate at aside opposite to the mounting table as viewed from the conductive plate;a conductive member connecting the one end of the conductive plate tothe ground plane; and a feeding line connected to the conductive plateat a point away from the one end of the conductive plate. As usedherein, substantially straight means a concept including not only astraight line but also a gentle curve.

Further, the conductive plate of the patch antenna may have the otherend, which is opposing to the one end connected to the conductivemember, folded toward the ground plane, and the conductive member of thepatch antenna may have one length in a same direction as the one end ofthe conductive plate formed shorter than the one end. With such aconfiguration, the patch antenna may be made smaller.

Still further, the antenna includes at least two conductive platesarranged on a same plane facing to the mounting surface of the mountingtable and each having two ends parallel to each other, the lengthbetween the two ends being at most approximately ¼ of a wavelength ofthe electromagnetic field in the antenna; and a ground plane arrangedfacing to the conductive plate at a side opposite to the mounting tableas viewed from the conductive plates; at least two conductive membersconnecting respective ends of the conductive plates to the ground plane;and at least two feeding lines connected to respective conductive platesat points away from respective ends of the conductive plates. Conductiveplates of the antenna are arranged such that the other end of oneconductive plate and the other end of the other conductive plate areperpendicular to each other. Feed lines of the antenna feed with phasesdifferent from each other. Thus, an electromagnetic field of a circularpolarization can be supplied into the processing container.

Still further, the antenna includes a plurality of conductive platesarranged on a same plane facing to the mounting surface of the mountingtable and each having substantially straight end, the length in adirection perpendicular to the one end being at most approximately ¼ ofa wavelength of the electromagnetic field in the antenna; and a groundplane arranged facing to the conductive plates at a side opposite to themounting table as viewed from the conductive plates; a plurality ofconductive members connecting respective ends of the conductive platesto the ground plane; and a plurality of feeding lines connected torespective conductive plates at points away from respective ends of theconductive plates. The plurality of conductive plates of the antenna arearranged with equal intervals around the center of the antenna withrespective one end oriented inward and respective other end, which areopposite to the one end, oriented outward. The plurality of feedinglines of the antenna feed corresponding conductive plate with the samephase. Thus, an electromagnetic field of substantial TM01 mode can besupplied inside the processing container.

In order to achieve the object above, a plasma apparatus according tothe present invention is characterized by an forming an antenna forsupplying an electromagnetic field of a high frequency wave into aprocessing container by a monopole antenna. When a wavelength of theelectromagnetic field on the antenna is given as λg, then the monopoleantenna can be formed with the size of approximately λ/4, at most, andit can still emit a high frequency wave equivalent to that emitted by adipole antenna. Accordingly, a processing container having a diameter Lof less than λg/2 or a high frequency wave of which frequency is lowerthan approximately c/(2 L) (where c is the speed of light) can beutilized.

Here, it is preferable to use a patch antenna as the monopole antenna.By using the patch antenna, the magnetic current forming portion can bemade longer to improve the radiation efficiency of the high frequencywave.

The patch antenna may include a conductive plate arranged facing to amounting table and having substantially straight one end, a length in adirection perpendicular to the one end being at most approximately ¼ ofa wavelength of an electromagnetic field in the patch antenna; a groundplane arranged facing to the conductive plate at a side opposite to themounting table as viewed from the conductive plate; a conductivematerial connecting the one end of the conductive plate to the groundplane; and a feeding line connected to a point away from the one end ofthe conductive plate.

Here, the conductive plate of the patch antenna may have other endopposing to the one end connected to the conductive material foldedtoward the ground plane. The conductive material of the patch antennahas one length in the same direction as the one end of the conductiveplate formed shorter than the one end of the conductive plate. With sucha configuration, the patch antenna can be made smaller. Further, adielectric plate may be arranged between the conductive plate and theground plate. This shortens the wavelength of the electromagnetic fieldon the conductive plate to further reduce the size of the antenna.

In order to achieve the object above, a plasma apparatus according tothe present invention is characterized by an antenna supplying a highfrequency wave into a processing container including a conductive platearranged facing to the mounting table arranged in the processingcontainer; a ground plane arranged facing to the conductive plate at aside opposite to the mounting table as viewed from the conductive plate;and a plurality of first feeding lines connected to the conductiveplate. Two each of the first feeding lines are connected away from eachother to at least one first line on the conductive plate perpendicularto a periphery of the conductive plate. Each first line has a length ofapproximately (N+½)×λg (N is an integer at least 0), where λg is awavelength of an electromagnetic field between the conductive plate andthe ground plane. As used herein, the first line perpendicular to theperiphery of the conductive plate is a line parallel to one edge of aquadrangle when the two-dimensional shape of the conductive plate is aquadrangle, and it is a line passing through the center of a circle whenthe two-dimensional shape of the conductive plate is a circle.

Two first feeding lines are connected on one first line on theconductive plate. As the length of the first line is approximately(N+½)×λg, the currents supplied from these two feeding lines oscillateson the first line to be a standing wave. Here, the feeding performed bythe two feeding lines defines the mode of the standing wave. As thevoltage waveform on the first line will have antinodes at opposing endswith the number of waves being N+½, the voltage variations at opposingends show opposite phases with respect to each other. Accordingly, alongopposing ends of the first line, magnetic currents are generated inreverse directions with respect to each other as viewed from the centerof the conductive plate. Accordingly, in this antenna, the TM11 mode isselectively excited. In TM11 mode, the directivity of a high frequencywave will be perpendicular to the main surface of the conductive plate,and therefore the high frequency wave is oriented directly to mountingtable for mounting an object to be processed. Therefore, the powerabsorbed by the processing container or the like can be reduced toincrease the power contributing to the plasma generation.

Here, the first line on the conductive plate forming the antenna may beset to pass through the center of the conductive plate. This preventsthe current from passing in the direction perpendicular to the firstline on the conductive plate, and therefore the radiation of the highfrequency wave in this direction can be suppressed.

Further, in the plasma apparatus above, the antenna may further includea plurality of second feeding lines connected to said conductive plate.Two each of the second feeding lines are connected away from each otherto at least one second line on said conductive plate perpendicular tocorresponding first line. The length of each second line isapproximately (M+½)×λg (M is an integer at least 0). Each second feedingline feeds with a same degree of phase lag behind corresponding firstfeeding line, such that the high frequency wave becomes a circularpolarization. In this case, according to the same principle as above,the TM11 mode is excited also in the second line direction. Further, bymaking the high frequency wave supplied from the antenna into theprocessing container to a circular polarization to rotate theelectromagnetic field around an axis perpendicular to a mounting surfaceof a mounting table for mounting an object to be processed, thedistribution of plasma generated by the electromagnetic field alsorotates. Thus, the uniformity of the plasma distribution when averagedby time can be improved.

Here, the high frequency wave supplied from the antenna is notnecessarily a perfectly circular polarization, and it may be a circularpolarization with a polarization ratio of at least 50%, preferably atleast 70%.

Here, the first and second lines on the conductive plate forming theantenna may be set to pass through the center of the conductive plate.Thus, the current supplied from the first feeding line may not passthrough the second line on the conductive plate, and conversely, thecurrent supplied from the second feeding line may not pass through thefirst line on the conductive plate. Then, generation of a circularpolarization reverse to a desired polarization (cross polarization) canbe hindered.

Further, the distance between two first feeding lines connected on thesame first line, or the distance between two second feeding linesconnected on the same second line may be set to λg/2. This wouldfacilitate designing the antenna.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a configuration of an etching apparatus according to afirst embodiment of the present invention.

FIG. 2A is a plan view showing an exemplary configuration of aconductive plate of a patch antenna shown in FIG. 1.

FIG. 2B shows coordinate systems.

FIGS. 3A and 3B are conceptual illustrations of a time-averaged electricfield distribution formed by the patch antenna shown in FIG. 1.

FIG. 4 is a cross sectional view showing a variation of the patchantenna shown in FIG. 1.

FIG. 5 shows polarization ratio of a circular polarization.

FIG. 6 shows a phase difference dependency of a polarization ratio of acircular polarization.

FIG. 7 shows a configuration of an etching apparatus according to asecond embodiment of the present invention.

FIG. 8 is a plan view showing an exemplary configuration of a conductiveplate of a patch antenna shown in FIG. 7.

FIGS. 9A and 9B are plan views showing other exemplary configurations ofa conductive plate of the patch antenna shown in FIG. 7.

FIG. 10 is a cross sectional view showing part of a configuration of anetching apparatus according to a third embodiment of the presentinvention.

FIG. 11 shows a two-dimensional configuration of an antenna viewed fromthe direction of line II-II′ in FIG. 10 and an exemplary configurationof a feeding system thereof.

FIG. 12A is a perspective view showing a configuration of a patchantenna forming the antenna shown in FIG. 10.

FIG. 12B shows coordinate systems.

FIGS. 13A and 13B illustrate principle of radiation of anelectromagnetic field by the patch antenna shown in FIG. 12A.

FIG. 14 is a conceptual illustration showing a manner of a magneticcurrent formed by a patch antenna at a certain moment.

FIG. 15 shows a polarization ratio of a circular polarization.

FIG. 16 shows a phase difference dependency of a polarization ratio of acircular polarization.

FIGS. 17A and 17B show a configuration of a variation of the patchantenna shown in FIGS. 12A and 12B.

FIG. 18 shows a two-dimensional configuration of an antenna used in anetching apparatus according to a fifth embodiment of the presentinvention and an exemplary configuration of a feeding system thereof.

FIG. 19 is a conceptual illustration showing a manner of a magneticcurrent formed by a patch antenna at a certain moment.

FIGS. 20A and 20B are conceptual illustrations of a field intensitydistribution formed by the antenna shown in FIG. 18.

FIG. 21 shows a configuration of an etching apparatus according to asixth embodiment of the present invention.

FIG. 22A is a perspective view showing a configuration of the patchantenna shown in FIG. 21.

FIG. 22B shows coordinate systems.

FIGS. 23A and 23B illustrate principle of radiation of anelectromagnetic wave by the patch antenna shown in FIG. 21.

FIG. 24 shows a configuration of a variation of the patch antenna shownin FIG. 21.

FIG. 25A shows a configuration of another variation of the patch antennashown in FIG. 21.

FIG. 25B shows coordinate systems.

FIG. 26 shows a configuration of an etching apparatus according to aneighth embodiment of the present invention.

FIG. 27A is a plan view of a patch 4032 in FIG. 26 viewed from itsbottom.

FIG. 27B shows a voltage waveform in x direction in FIG. 27A.

FIG. 27C shows coordinate systems.

FIG. 28 is a plan view showing a variation of the patch.

FIG. 29 is a cross sectional view showing a variation of a patchantenna.

FIG. 30 shows a variation of a patch antenna.

FIG. 31 shows a configuration for generating a circular polarizationusing a patch antenna shown in FIG. 26.

FIGS. 32A, 32B and 32C illustrate operating principle of a patch antennawith four-point feeding.

FIGS. 33A and 33B are conceptual illustrations showing an electric fielddistribution formed by the patch antenna shown in FIG. 26.

FIG. 34 illustrates a polarization ratio of a circular polarization.

FIG. 35 shows a phase difference dependency of a polarization ratio of acircular polarization.

FIG. 36 shows a variation of a patch antenna.

FIGS. 37A and 37B show an exemplary configuration of a conventionalpatch antenna used for a high frequency plasma processing apparatus.

FIG. 37C shows coordinate systems.

FIGS. 38A and 38B illustrate principle of radiation of anelectromagnetic field by the patch antenna shown in FIGS. 37A-37C.

FIGS. 39A and 39B are conceptual illustrations of a field intensitydistribution formed by the patch antenna shown in FIGS. 37A-37C.

FIG. 40 is a plan view of a dipole antenna conventionally used in aplasma apparatus.

FIG. 41 is a cross sectional view showing an exemplary configuration ofan etching apparatus using a conventional high frequency plasmaapparatus.

FIG. 42A shows a configuration of a patch antenna shown in FIG. 41.

FIG. 42B shows coordinate systems.

FIGS. 43A and 43B illustrate operating principle of the patch antennashown in FIG. 41.

BEST MODES FOR CARRYING OUT THE INVENTION

In the following, embodiments of a first invention of the presentinvention will be described in detail with reference to the drawings.Here, an example in which a plasma apparatus in accordance with thefirst invention is applied to an etching apparatus will be described.

First Embodiment

FIG. 1 shows a configuration of an etching apparatus in accordance witha first embodiment of the present invention. FIG. 1 shows some parts incross section.

The etching apparatus shown in FIG. 1 has a cylindrical processingcontainer 11 that is open at an upper portion. Processing container 11is formed of a conductive member such as aluminum.

At the upper opening of processing container 11, a dielectric plate 12formed of quartz glass or ceramic (such as Al₂O₃ or AlN) having athickness of about 20-30 mm is arranged. At a joint portion betweenprocessing container 11 and dielectric plate 12, a sealing member 13such as an O-ring is interposed, to ensure air-tightness insideprocessing container 11.

At the bottom of processing container 11, an insulating plate 14 formedof ceramic or the like is provided. Further, an exhaust port 15 isprovided penetrating through insulating plate 14 and the bottom ofprocessing container 11 and, by means of a vacuum pump (not shown)communicated with exhaust port 15, the inside of processing container 11can be evacuated to a desired degree of vacuum.

At upper portion and lower portion of a sidewall of processing container11, a plasma gas supply nozzle 16 is provided for introducing a plasmagas such as Ar and a processing gas supply nozzle 17 is provided forintroducing an etching gas into processing container 11, respectively.Plasma gas supply nozzle 16 and processing gas supply nozzle 17 areformed by a quartz pipe or the like.

In processing container 11, a mounting table 22 is contained, on anupper surface of which a substrate 21 to be etched (the object to beprocessed) is placed. Mounting table 22 is supported by an elevatingshaft 23 passing, with a play, through the bottom of processingcontainer 11 to be freely movable upward and downward. Further, mountingtable 22 is connected to a biasing high frequency power supply 26through a matching box 25. In order to ensure air-tightness ofprocessing container 11, a bellows 24 is provided to surround elevatingshaft 23, between mounting table 22 and insulating plate 14.

Above dielectric plate 12, a patch antenna 1030 is arranged forsupplying a high frequency wave into processing container 11 throughdielectric plate 12. Patch antenna 1030 is separated from processingcontainer 11 by dielectric plate 12, and protected from the plasmagenerated in processing container 11. Further, a shield member 18 coversperipheries of dielectric plate 12 and patch antenna 1030.

Patch antenna 1030 has a ground plane 1031 made of a grounded conductiveplate, and a conductive plate 1032 forming a resonator. Conductive plate1032 is arranged facing to ground plane 1031 with a prescribed distance,which is maintained by a conductive cylinder 1031 connecting each centerof ground plane 1031 and conductive plate 1032. Ground plane 1031,conductive plate 1032 and conductive cylinder 1031 are formed of copper,aluminum or the like. Patch antenna 1030 with such a configuration isarranged such that conductive plate 1032 is located at the bottom sidethereof facing to dielectric plate 12.

FIGS. 2A and 2B show an exemplary configuration of conductive plate1032. FIG. 2A is a plan view of conductive plate 1032 in FIG. 1 viewedfrom the bottom, while FIG. 2B shows coordinate systems. Conductiveplate 1032 has a two-dimensional shape of a square with each edge beingapproximately λg/2. λg means the wavelength of an electromagnetic fieldin patch antenna 1030. Here, it is assumed that a center O of conductiveplate 1032 is at the origin of coordinate systems, and edges ofconductive plate 1032 are parallel to x axis and y axis, respectively.In this case, two feeding points P, Q of conductive plate 1032 areprovided at two points on x axis and y axis away from center O byapproximately equal distances, respectively.

As shown in FIG. 1, two coaxial lines 1041A and 1041B are employed forfeeding patch antenna 1030. Outer conductors 1042A and 1042B of coaxiallines 1041A and 1041B are connected to ground plane 1031, while innerconductors (feeding lines) 1043A and 1043B of coaxial lines 1041A and1041B penetrate through an opening of ground plane 1031 to be connectedto conductive plate 1032 at feeding points P, Q thereon, respectively.It is noted that, coaxial line 1041B is longer in electrical length thancoaxial line 1041A by 90°.

These coaxial lines 1041A and 1041B are connected to feeding highfrequency power supply 45 through matching boxes 1044A and 1044B,respectively. From high frequency power supply 45, a high frequency waveof 100 MHz-8 GHz is output. Additionally, by providing matching boxes 44for impedance matching, efficiency of power use can be improved.

Next, an operation of the etching apparatus shown in FIG. 1 will bedescribed.

The inside of processing container 11 is evacuated, for example, to adegree of vacuum of about 0.1-10 Pa, with substrate 21 placed on theupper surface of mounting table 22. While maintaining the degree ofvacuum, Ar as the plasma gas is supplied from plasma gas supply nozzle16, and CF₄ as the etching gas is supplied from processing gas supplynozzle 17, with the flow rate thereof being controlled.

In the state where the plasma gas and the etching gas are suppliedinside processing container 11, two feeding points P, Q on conductiveplate 1032 of patch antenna 1030 are fed at a voltage of an equalamplitude. Here, since coaxial line 1041B is longer in electrical lengththan axial line 1041A by 90°, the feeding phase of feeding point Q lagsbehind feeding point P by 90°.

The current supplied to feeding point P oscillates in x axis direction,and emits a high frequency wave of a linear polarization parallel to xaxis, according to the same principle as described with reference toFIGS. 38A and 38B. On the other hand, the current supplied to feedingpoint Q oscillates in y axis direction, and similarly emits a highfrequency wave of linear polarization parallel to y axis. It is notedthat this linear polarization parallel to y axis lags 90° behind thelinear polarization parallel to x axis. These two linear polarizationsare equal in amplitude, perpendicular to each other spatially, andhaving different phases from each other by 90°, and therefore, theybecome circular polarization. In the positive direction of z axis shownin FIG. 2B, they become right-hand circular polarization.

Thus, the high frequency wave emitted from patch antenna 1030 becomesthe circular polarization, passes through dielectric plate 12 andintroduced into processing container 11. The high frequency wave formsan electric field in processing container 11 to cause electrolyticdissociation of Ar, and thus generates plasma in upper space A abovesubstrate 21 to be processed.

In this etching apparatus, since negative potential is biased onmounting table 22, therefore ions are extracted from the plasma beinggenerated, and used for the etching process for substrate 21.

FIGS. 3A and 3B are conceptual illustrations of a time-averaged electricfield distribution formed by patch antenna 1030. FIG. 3A shows theelectric field distribution in xz plane, while FIG. 3B shows theelectric field distribution in yz plane. As above, since the highfrequency wave emitted by patch antenna 1030 becomes the circularpolarization, the electric field distribution thereof will besubstantially uniform over xz plane and yz plane, as shown in FIGS. 3Aand 3B. As compared to the electric field distribution formed by aconventional patch antenna shown in FIGS. 39A and 39B, it is apparentthat the electric field distribution has been improved.

The generation of plasma with the electromagnetic field having such aspatial distribution makes the distribution of plasma uniform, thereforethe etching process can be performed at uniform speed over the entiresubstrate 21.

The two-dimensional shape of conductive plate 1032 may be a 90°rotationally symmetrical shape (a shape that overlaps when rotated by90° around a central axis of conductive plate 1032) such as a circle, inaddition to the square form shown in FIG. 2A. It is noted that whenemploying a circle, diameter thereof may be 1.17 λg/2.

Further, the two-dimensional shape of conductive plate 1032 may be ashape in which its lengths in two directions perpendicular to each otherviewed from its center O are different, e.g., a rectangle. In this case,the feeding phase difference between two feeding points P, Q may not be90°, and it is adjusted by the lengths in the two directions describedabove.

Still further, in the etching apparatus shown in FIG. 1, it has beendescribed that the right-hand circular polarization is emitted in thepositive direction of z axis shown in FIG. 2B. To emit the left-handcircular polarization, coaxial line 1041A may be set to have anelectrical length longer than coaxial line 1041B by 90°, conversely.

Still further, ground plane 1031 and conductive plate 1032 forming thepatch antenna may be formed at two opposing surfaces of dielectric plate34 made of ceramic or the like, as shown in FIG. 4. Thus, the patchantenna can be made smaller.

Still further, the high frequency wave emitted by the patch antenna isnot necessarily a perfect circular polarization. Given that thepolarization ratio of a circular polarization of which length of longaxis is 2 a and that of short axis is 2 b as shown in FIG. 5 is b/a(×100)%, generation of the circular polarization with a polarizationratio of at least 50%, preferably at least 70% results in theimprovement of the plasma distribution.

Here, a method for adjusting the polarization ratio of a circularpolarization is described briefly.

First, when two linear polarizations perpendicular to each other are outof phase to each other by 90° but with different amplitude values, giventhat the two linear polarizations are expressed as a sin (ωt+π/2), b sin(ωt), then the polarization ratio is simply determined by the amplitudevalue ratio b/a (×100)%. Therefore, in order to obtain the polarizationratio of at least 70%, the amplitude value ratio may only be set to atleast 70%.

Additionally, when two linear polarizations perpendicular to each otherare equal in amplitude value but with a phase difference other than 90°,given that the two linear polarizations are expressed as sin (ωt−θ), sin(ωt), then the phase difference dependency of the polarization ratiowhen the phase difference θ takes on the value in the vicinity of 90°will be as shown in FIG. 6. Therefore, in order to obtain thepolarization ratio of at least 70%, the phase difference θ may only beadjusted to approximately 70°-110°.

Second Embodiment

Next, a second embodiment of the present invention will be described. Inthe first embodiment, though it has been described to emit a circularpolarization by feeding patch antenna 1030 at two points thereof, it isalso possible to emit a circular polarization by feeding at only onepoint.

FIG. 7 shows a configuration of an etching apparatus according to thesecond embodiment of the present invention. In the figure, portionssimilar to those of FIG. 1 will be denoted by the same referencecharacters and description thereof will appropriately be omitted.

A patch antenna 1230 shown in FIG. 7 includes a ground plane 1231, aconductive plate 1232 forming a resonator, and a conductive cylinder 233connecting a center O of conductive plate 1232 to ground plane 1231.

FIG. 8 is a plan view showing an exemplary configuration of conductiveplate 1232, which illustrates a two-dimensional shape of conductiveplate 1232 in FIG. 7 viewed from the bottom. In this figure, portionsimilar to those of FIGS. 2A, 2B will be denoted by the same referencecharacters and description thereof will appropriately be omitted.

The two-dimensional shape of conductive plate 1232 corresponds to circle1232A of which peripheral regions are cut out partially. Morespecifically, two regions in the vicinity where circumference and y axiscross are cut out in quadrangular forms. The area to be the cut out maybe approximately 3% of circle 1232A. It is assumed that the length in xdirection of conductive plate 1232 is 1.17×λg/2, while the length in yaxis direction thereof is 1.17×λg/2−2 d.

A feeding point V is provided at one point on the straight line thatcrosses x axis and y axis at the angle of 45°. As shown in FIG. 7, tofeeding point V, an inner conductor 1043 of coaxial line 1041 connectedto high frequency power supply 45 is connected.

The current supplied from high frequency power supply 45 to feedingpoint V of conductive plate 1232 will flow in x axis direction and yaxis direction, independently. Here, since y axis direction is shorterthan 1.17×λg/2 by 2 d, the permittivity in the electric magnetic fieldbecomes greater, causing the phase lag of the current passing in y axisdirection. By setting the value of 2 d and the length of the cut outportion such that the phase lag of 90° can be obtained, the current canbe passed in x and y axis directions of conductive plate 1232 with thephase lag of 90°. Thus, the circular polarization can be emitted frompatch antenna 1230.

While it has been described that feeding point V is provided at onepoint on a straight line crossing x axis and y axis at the angle of 45°,it may be provided at one point in a direction between x axis directionand y axis direction, if a perfectly circular polarization is notrequired.

The two-dimensional shape of conductive plate 1232 is not limited to theshape shown in FIG. 8, and it may be at least the shape in which twodirections perpendicular to each other viewed from center O ofconductive plate 1232 are different. Accordingly, it may be an ellipseas shown in FIG. 9A. Additionally, as shown in FIG. 9B, it may be aquadrangle in which the length of long edge L1 is approximately λg/2,while the length of short edge L2 is less than approximately λg/2.

Further, similarly to the first embodiment, a dielectric plate formed ofceramic or the like as shown in FIG. 4 may be provided between groundplane 1231 and conductive plate 1232. Thus, the patch antenna can bemade smaller.

In the foregoing, though an example where the plasma apparatus accordingto the first invention is applied to an etching apparatus has beendescribed, it is needless to say that it may be applied to other plasmaapparatuses such as a plasma CVD apparatus.

As described above, the plasma apparatus according to the firstinvention uses the antenna having the conductive plate forming theresonator and the ground plane arranged facing to the conductive plate,to make the high frequency wave emitted from the antenna to be acircular polarization. Thus, the spatial distribution of theelectromagnetic field in the processing container, and therefore thedistribution of plasma, becomes uniform as compared to the conventionalmanner.

In the following, referring to the figures, embodiment according to asecond invention of the present invention will be described in detail.Here, an example will be described where a plasma processing apparatusaccording to the second invention is applied to an etching apparatus.

Third Embodiment

FIG. 10 is a cross-sectional view showing part of the configuration ofan etching apparatus according to a third embodiment of the presentinvention.

The etching apparatus shown in FIG. 10 has a cylindrical processingcontainer 11 that is open at an upper portion. Processing container 11is formed of a conductive member such as aluminum.

At the upper opening of processing container 11, a dielectric plate 12formed of quartz glass or ceramic (for example, Al₂O₃ or AlN) having athickness of about 20-30 mm is arranged. At a joint portion betweenprocessing container 11 and dielectric plate 12, a sealing member 13such as an O-ring is interposed, to ensure air-tightness insideprocessing container 11.

At the bottom of processing container 11, an insulating plate 14 formedof ceramic or the like is provided. Further, an exhaust port 15 isprovided penetrating through insulating plate 14 and the bottom ofprocessing container 11 and, by means of a vacuum pump (not shown)communicated with exhaust port 15, the inside of processing container 11can be evacuated to a desired degree of vacuum.

At upper portion and lower portion of a sidewall of processing container11, a plasma gas supply nozzle 16 is provided for introducing a plasmagas such as Ar and a processing gas supply nozzle 17 is provided forintroducing an etching gas into processing container 11, respectively.Plasma gas supply nozzle 16 and processing gas supply nozzle 17 areformed by a quartz pipe or the like.

In processing container 11, a mounting table 22 is contained, on anupper surface (a mounting surface) of which a substrate 21 to be etched(the object to be processed) is placed. Mounting table 22 is supportedby an elevating shaft 23 passing, with a play, through the bottom ofprocessing container 11 to be freely movable upward and downward.Further, mounting table 22 is connected to a biasing high frequencypower supply 26 through a matching box 25. Output frequency of highfrequency power supply 26 is a prescribed frequency within the range ofseveral hundred kHz to ten and several MHz. In order to ensureair-tightness of processing container 11, a bellows 24 is-provided tosurround elevating shaft 23, between mounting table 21 and insulatingplate 14.

Above dielectric plate 12, an antenna 2030 is arranged for supplying anelectromagnetic field of a high frequency wave into processing container11 through dielectric plate 12. Antenna 2030 is separated fromprocessing container 11 by dielectric plate 12, and protected from theplasma generated in processing container 11. Further, a shield member 18covers peripheries of dielectric plate 12 and antenna 2030 to preventleakage of the electromagnetic field emitted from antenna 2030 to theoutside of the etching apparatus.

FIG. 11 shows a two-dimensional configuration of antenna 2030 in FIG. 10viewed from the bottom, and an exemplary configuration of feeding systemthereof. Antenna 2030 is formed by combining four monopole patchantennas 2030A, 2030B, 2030C, and 2030D each having a conductive plate2032 having a trapezoid shape in two dimensions. Here, of two paralleledges of conductive plate 2032, the shorter edge and the longer edge aredenoted as ends 2032A and 2032B, respectively. Then, patch antennas2030A-2032D are arranged with equal intervals around center O of antenna2030, with each end 2032A directed inward, and end 2032B directedoutward. As shown in FIG. 10, it is arranged such that conductive plate2032 is located at the bottom facing to dielectric plate 12.

For feeding patch antennas 2030A-2030D, coaxial lines 2041A, 2041B,2041C and 2041D are employed, respectively.

Four patch antennas 2030A-2030D forming antenna 2030 have identicalconfigurations. Here, patch antennas 2030A-2030D are collectivelydenoted as patch antenna 2030X (X refers to A, B, C and D). Further,coaxial lines 2041A-2041D are collectively denoted as coaxial line 2041X(X refers to A, B, C, and D). FIGS. 12A and 12B show a configuration ofpatch antenna 2030X. Here, FIG. 12A is a perspective view, while FIG.12B shows coordinate systems.

As shown in FIG. 12A, patch antenna 2030X includes a ground plane 2031formed of a grounded conductive plate, a conductive plate 2032 forming aresonator and having a two-dimensional shape of a trapezoid, and aconductive member 2033 connecting end 2032A of conductive plate 2032 toground plane 2031.

For ease of description, coordinate systems are defined as follows xaxis is set in the direction of the height of the trapezoid ofconductive plate 2032, y axis is set in a direction parallel to theparallel two edges of the trapezoid, and z axis is set in the positivedirection of conductive plate 2032 leading from ground plane 2031 towardconductive plate 2032.

Conductive plate 2032 forming a resonator is arranged facing to andparallel to ground plane 2031. Conductive plate 2032 has a shape oftrapezoid as described above, and when the wavelength of theelectromagnetic field between conductive plate 2032 and ground plane2031 is given as λg, then the height of the trapezoid (specifically, thelength in x axis direction perpendicular to end 2032A) is set toapproximately λg/4. Additionally, the length of end 32B of conductiveplate 2032 is desirably less than approximately λg/2.

Conductive member 2033 connecting end 2032A of conductive plate 2032 toground plane 2031 is a plate-like member provided perpendicular toground plane 2031. The length of conductive member 2033 in y axisdirection is equal to that of end 2032A of conductive plate 2032, andthe length in z axis direction (i.e., height) is desirably 5-50 mm,approximately.

End 2032A of conductive plate 2032 is short-circuited to ground plane2031 by conductive member 2033, and therefore the potential of end 2032Ais fixed to 0 (zero) even when being fed from coaxial line 2041X. Hence,end 2032A is referred to as fixed end 2032A. On the other hand, end 32Bopposing to fixed end 2032A with a distance of λg/4 is open, and henceit is referred to as open end 32B.

It is noted that ground plane 2031 is a member shared by patch antennas2030A-2030D, and have a circular shape similarly to dielectric plate 12.

Ground plane 2031, conductive plate 2032 and conductive member 2033 areformed of copper, aluminum or the like.

Here, the principle of radiation of electromagnetic field by patchantenna 2030X is described. FIGS. 13A and 13B are illustrationstherefor. FIG. 13A shows conductive plate 2032, while FIG. 13B shows thevoltage distribution in x axis direction in conductive plate 2032.

The potential of fixed end 2032A of conductive plate 2032 is fixed to 0(zero), and that the length of conductive plate 2032 in x axis directionis λg/4. Therefore, the current supplied from high frequency powersupply 45 to conductive plate 2032 behaves as if the length ofconductive plate 2032 in x axis direction is λg/2, oscillating in x axisdirection to be a standing wave. Here, the voltage waveform repeats thechange shown by a solid line and a dotted line in FIG. 13B.

When the voltage at open end 32B of conductive plate 2032 is positive,the line of electric force is directed from conductive plate 2032 towardground plane 2031 as indicated by the solid line in FIG. 13A, and whenthe voltage at open end 32B of conductive plate 2032 is negative, theline of electric force is directed from ground plane 2031 towardconductive plate 2032 as indicated by the dotted line in FIG. 13B. Thedirection of the line of electric force is the same as the direction ofthe displacement current, and therefore a magnetic current repeating thechange shown by the solid line and the dotted line in FIG. 13A isgenerated along open end 2032B and parallel to y axis. Since anelectromagnetic field is emitted having the magnetic current as a wavesource, the electromagnetic field becomes a linear polarization parallelto x axis.

Patch antenna 2030X has an excellent radiation efficiency of theelectromagnetic field due to its long open end 32B that functions as amagnetic current forming portion. From the view point of the radiationefficiency, the length of conductive plate 2032 in y axis directionshould be longer. In order to decrease the effect of the magneticcurrent formed in the side face of patch antenna 2030X parallel to xaxis, the length of conductive plate 2032 in y axis direction ispreferably set to at least λg/8, approximately.

On the other hand, as shown in FIG. 12A, outer conductor 2042X ofcoaxial line 2041X (X refers to A, B, C, and D) is connected to groundplane 2031, while inner conductor (feeding line) 43X of coaxial line2041X (X refers to A, B, C, and D) penetrates through the opening ofground plane 2031 to be connected to feeding point P on conductive plate2032. Feeding point P is provided at a point away from fixed end 2032Aof conductive plate 2032. Considering impedance matching and the like,it is desirable to set feeding point P near the center of conductiveplate 2032.

As shown in FIG. 11, coaxial lines 2041A-2041D respectively connected topatch antennas 2030A-2030D are connected to feeding high frequency powersupply 45. It is noted that the electrical lengths of coaxial lines2041A-2041D are each longer by multiples of 90°, with reference tocoaxial line 2041A. Specifically, when the electrical length of coaxialline 2041A is θ, electrical length of coaxial lines 2041B, 2041C and2041D are θ+90°, θ+180°, and θ+270°, respectively. Thus, feedings topatch antennas 2030A-2030D are performed with a phase difference of 90°each. Here, patch antennas 2030A-2030D are fed with equal power.

It is noted that output frequency of feeding high frequency power supply45 is a prescribed frequency in a range of about 100 MHz-8 GHz.Additionally, by interposing matching boxes 2044A, 2044B, 2044C, and2044D for impedance matching in coaxial lines 2041A-2041D, respectively,efficiency of power use can be improved.

Next, an operation of the etching apparatus shown in FIG. 10 will bedescribed.

The inside of processing container 11 is evacuated, for example, to a,degree of vacuum of about 0.01-10 Pa, with substrate 21 placed on theupper surface of mounting table 22. While maintaining the degree ofvacuum, Ar as the plasma gas is supplied from plasma gas supply nozzle16, and CF₄ as the etching gas is supplied from processing gas supplynozzle 17, with the flow rate thereof being controlled.

In the state where the plasma gas and the etching gas are suppliedinside processing container 11, feeding from high frequency power supply45 to antenna 2030 is initiated. At this time, patch antennas2030A-2030D are fed with a phase difference of 90° each.

FIG. 14 is a conceptual illustration showing the manner of magneticcurrent formed by patch antennas 2030A-2030D at a certain moment. Thefeeding phase difference between patch antennas 2030A and 2030C is 180°,therefore patch antennas 2030A and 2030C form magnetic currents in thesame direction parallel to y axis. Thus, patch antennas 2030A and 2030Ceach emit a linear polarization of the same phase parallel to x axis.Similarly, the feeding phase difference between patch antennas 2030B and2030D is 180°, therefore patch antennas 2030B and 2030D each emit alinear polarization of the same phase parallel to y axis. In addition,since the feeding phase difference between patch antennas 2030A and2030B (or between 2030C and 2030D) is 90° C., the phase differencebetween the linear polarization in x axis direction and that of y axisdirection is 90°. These two linear polarizations are equal in amplitude,perpendicular to each other spatially, and have a the phase differenceof 90°, and therefore a circular polarization is formed.

Thus, the electromagnetic field emitted from patch antenna 2030 formsthe circular polarization, passes through dielectric plate 12 andintroduced into processing container 11. Then, formation of electricfield in processing container 11 causes electrolytic dissociation of Ar,and thus generates plasma in upper space A above substrate 21 to beprocessed. The plasma diffuses into processing container 11, and has itsenergy and anisotropy controlled by a bias voltage applied to mountingtable 22, and utilized for the etching process.

The field intensity distribution by linear polarizations emitted bypatch antennas 2030A and 2030C (or patch antennas 2030B and 2030D) isbiased as in FIGS. 39A and 39B. However, by forming a circularpolarization to rotate the electric field around an axis perpendicularto mounting table 22, the plasma distribution generated by this electricfield also rotates, and therefore the etching process can be performeduniform when averaged by time than the conventional manner.

Though an example has been described where four patch antennas2030A-2030D are employed to make the electromagnetic field to be acircular polarization, the number of patch antenna 2030X for forming acircular polarization may be at least two.

Additionally, the electromagnetic field supplied to processing container11 is not necessarily a perfectly circular polarization. Given that thepolarization ratio of a circular polarization of which length of longaxis is 2 a and that of short axis is 2 b as shown in FIG. 15 is b/a(×100)%, generation of circular polarization with a polarization ratioof at least 50%, preferably at least 70% results in the improvement ofthe uniformity over a plane in processing.

Here, a method for adjusting the polarization ratio of a circularpolarization is described briefly.

First, when two linear polarizations perpendicular to each other are outof phase to each other by 90° but with different amplitude values, giventhat the two linear polarizations are expressed as a sin(ωt+π/2), bsin(ωt), then the polarization ratio is simply determined by theamplitude value ratio b/a (×100)%. Therefore, in order to obtain thepolarization ratio of at least 70%, the amplitude value ratio may onlybe set to at least 70%.

Additionally, when two linear polarizations perpendicular to each otherare equal in amplitude value but with a phase difference other than 90°,given that the two linear polarizations are expressed as sin(ωt−θ),sin(ωt), then the phase difference dependency of the polarization ratiowhen the phase difference θ takes on the value in the vicinity of 90°will be as shown in FIG. 16. Therefore, in order to obtain thepolarization ratio of at least 70%, the phase difference θ may only beadjusted to approximately 70°-110°.

Though patch antenna 2030X shown in FIG. 12A has a two-dimensional shapeof a trapezoid, the shape thereof is only required to have straightfixed end 2032A and a length of approximately λg/4 in x axis directionperpendicular to fixed end 2032A. Accordingly, it may be a quadrangularor a semi-circular shape two-dimensionally. Still further, as shown inFIG. 18 that follows, a patch antenna in which open end of conductiveplate is circular arc may be employed. Still further, both of the openend and the fixed end may be circular arc.

Still further, a dielectric plate may be arranged between ground plane2031 and conductive plate 2032 forming patch antenna 2030X. Thus, thewavelength λg of the electromagnetic field between conductive plate 2032and ground plane 2031 become shorter, therefore patch antenna 2030X canbe made smaller.

Fourth Embodiment

Next, a variation of patch antenna 2030X shown in FIG. 12A will bedescribed. FIGS. 17A and 17B show a configuration of the variation. FIG.17A is a perspective view of patch antenna 2130X, while FIG. 17B showscoordinate systems. In these figures, portions similar to those of FIGS.12A and 12B are denoted by similar reference characters, and descriptionthereof will appropriately be omitted.

A patch antenna 2130X shown in FIG. 17A has, in the configuration ofpatch antenna 2030X shown in FIG. 12A, open end 2032B of conductiveplate 2032 folded in the direction of ground plane 2031, and conductivemember 2033 cut out partially to be a narrow shape.

In the following, description will be made in detail. In patch antenna2130X, the length of conductive plate 2132 forming a resonator in x axisdirection is at least approximately λg/8 and less than approximatelyλg/4.

Additionally, to conductive plate 2132, a conductive plate 2134extending from open end 2132B toward ground plane 2031 is connected. Thelength of conductive plate 2134 in y axis direction is the same as thatof conductive plate 2132, while the length thereof in z axis directionis shorter than that of conductive member 2133. Accordingly, the tip ofconductive plate 2134 does not contact ground plane 2031. Further,conductive plate 2134 is made of the same material as conductive plate2132 and the like, i.e., copper or aluminum.

Still further, conductive member 2133 connecting fixed end 2132A ofconductive plate 2132 to ground plane is shorter in y axis directionthan conductive plate 2132.

When patch antenna 2130X with such a configuration is fed, largecapacitance is formed between conductive plate 2134 and ground plane2031. Additionally, large inductance is formed in the narrow conductivemember 2133. By designing the apparatus such that these capacitance andinductance compensate each other, the length of conductive plate 2132 inx axis direction can be shortened to approximately λg/8, and the patchantenna can be made smaller. Conversely, since it allows to emit anelectromagnetic field of a lower frequency wave by the same antennasize, the degree of freedom in designing the etching apparatus, of whichantenna size has been limited by the diameter of processing container11, can be increased.

On the other hand, patch antenna 2130X is capable of emitting theelectromagnetic field equivalent to those emitted by patch antenna 2030Xshown in FIG. 12A. Therefore, patch antenna 2130X can be used to form anantenna for supplying the electromagnetic field to achieve theuniformity over a plane, which is equivalent to those achieved by theprocess with the etching apparatus according to the third embodiment.

Fifth Embodiment

While the etching apparatus according to the third embodiment employs aplurality of patch antennas 2030X to make the electromagnetic fieldsupplied into processing container 11 to be a circular polarization, anetching apparatus according to a third embodiment makes theelectromagnetic field to be a substantial TM01 mode. The configurationof the etching apparatus according to the third embodiment thatcorresponds to FIG. 10 is similar to that of the third embodiment, andtherefore description thereof is omitted.

FIG. 18 shows a two-dimensional configuration of an antenna 2230 used inthe etching apparatus according to the fifth embodiment of the presentinvention, and an exemplary configuration of its feeding system. In thefigure, portions similar to those of FIG. 11 are denoted by the similarreference characters, and description thereof will appropriately beomitted.

Antenna 2230 is formed by combining four monopole patch antennas2230A-2230D. Though patch antennas 2230A-2230D as a whole are configuredsimilarly to patch antenna 2030X shown in FIG. 12A, the differencebetween them is that open end 2232B of conductive plate 2232 forming aresonator is formed in a circular arc. Preferably, when four patchantennas 2230A-2230D are arranged with equal intervals around center Oof antenna 2230 with each open end 2232B directed outward, the lineconnecting each open end 2232B forms a substantial circle. Here, thelength from fixed end 2232A to open end 2232B of each patch antenna2230A-2230D are approximately (1.17±0.05)×λg/4 on x axis or on y axis.

For feeding patch antennas 2230A-2230D, coaxial lines 2241A, 2241B,2241C, and 2241D are employed, respectively. The electrical lengths ofcoaxial lines 2241A-2241D are all equal, which is different from coaxiallines 2041A-2041D. Accordingly, patch antennas 2230A-2230D are all fedwith the same phase.

FIG. 19 is a conceptual illustration showing the manner of magneticcurrents formed by patch antennas 2230A-2230D at a certain moment. Aspatch antennas 2230A-2230D are fed with the same phase, patch antennas2230A-2230D form magnetic currents in the same direction along theirrespective open ends 2232B. Since the magnetic currents are formed onthe same circumference, the electric field of an electromagnetic fieldhaving the magnetic currents as the wave source is distributedapproximately radially around center O of antenna 2230. Here, the modeof the electromagnetic field showing such an electric field distributionis referred to as a substantial TM01 mode. The field intensitydistribution on xz plane and on yz plane of the substantial TM01 modewill be approximately uniform as shown in FIGS. 20A and 20B,respectively. As compared to the field intensity distribution formed bythe single patch antenna that operates like a dipole as shown in FIG.14, it is found that the field intensity distribution is improved byantenna 2230 shown in FIG. 18.

By generating plasma by the electric field having such a uniform spatialdistribution as shown in FIGS. 20A and 20B, the plasma distribution canbe made uniform. This enables to perform etching process at uniformspeed over the entire substrate 21.

Though the example has been described where four patch antennas2230A-2230D are employed to make the electromagnetic field to be thesubstantial TM01 mode, the substantial TM01 mode can be formed with atleast two patch antennas if they each have open end 2232B of conductiveplate 2232 of a circular arc. Further, an antenna may be formed with atleast three patch antennas 2030X having straight open end 32B ofconductive plate 2032 as shown in FIG. 12A.

Still further, in order to approximate the electromagnetic field emittedby antenna 2230 shown in FIG. 19 to a perfect TM01 mode, the intervalsbetween each of patch antennas 2230A-2230D may be set shorter.

Still further, a dielectric plate may be arranged between ground plane2031 and conductive plate 2232 forming patch antennas 2230A-2230D.

Still further, a patch antenna having the configuration as shown in FIG.17A may be employed. In this case, open end 2132B of conductive plate2132 may be shaped in a circular arc. Here, the length from fixed end2132A to open end 2232B is set to approximately at least 1.17×λg/8, andapproximately less than 1.7×λg/4 on x axis or on y axis.

In the foregoing, though the example has been described where the plasmaprocessing apparatus according to the second invention is applied to anetching apparatus, it is needless to say that it can be applied to otherplasma processing apparatus such as a plasma CVD apparatus.

As described above, in the plasma processing apparatus according to thesecond invention, the antenna formed by a plurality of monopole antennasis used to supply the electromagnetic field of the circular polarizationinto the processing container. The circular polarization rotates theelectromagnetic field around the axis perpendicular to the mountingsurface of the mounting table, to rotates the plasma distributiongenerated by this electromagnetic field as well. Thus, the plasmaprocess can be performed uniform when averaged by time as compared tothe conventional manner.

Further, the antenna formed by a plurality of monopole antennas is usedto supply the electromagnetic field of substantial TM01 mode intoprocessing container. The electric field in the substantial TM01 mode isdistributed approximately radially around the axis perpendicular to themounting surface of the mounting table, and therefore the uniformity ofthe plasma distribution on a plane that is parallel to the mountingsurface can be improved. Accordingly, the plasma process can beperformed uniform as compared to the conventional manner.

Still further, by using the patch antenna as a monopole antenna, theradiation efficiency of the electromagnetic field can be improved.

In the following, referring to the figures, embodiments according to athird invention of the present invention will be described in detail.Here, an example will be described where a plasma apparatus according tothe third invention is applied to an etching apparatus.

Sixth Embodiment

FIG. 21 shows a configuration of an etching apparatus according to asixth embodiment of the present invention. FIG. 21 shows a cross sectionfor part of the configuration.

The etching apparatus shown in FIG. 21 has a cylindrical processingcontainer 11 that is open at an upper portion. Processing container 11is formed of a conductive member such as aluminum.

At the upper opening of processing container 11, a dielectric plate 12formed of quartz glass or ceramic (for example, Al₂O₃, AlN or the like)having a thickness of about 20-30 mm is arranged. At a joint portionbetween processing container 11 and dielectric plate 12, a sealingmember 13 such as an O-ring is interposed, to ensure air-tightnessinside processing container 11.

At the bottom of processing container 11, an insulating plate 14 formedof ceramic or the like is provided. Further, an exhaust port 15 isprovided penetrating through insulating plate 14 and the bottom ofprocessing container 11 and, by means of a vacuum pump (not shown)communicated with exhaust port 15, the inside of processing container 11can be evacuated to a desired degree of vacuum.

At upper portion and lower portion of a sidewall of processing container11, a plasma gas supply nozzle 16 is provided for introducing a plasmagas such as Ar and a processing gas supply nozzle 17 is provided forintroducing an etching gas into processing container 11, respectively.Plasma gas supply nozzle 16 and processing gas supply nozzle 17 areformed by a quartz pipe or the like.

In processing container 11, a mounting table 22 is contained, on anupper surface of which a substrate 21, such as a wafer to be etched, isplaced. Mounting table 22 is supported by an elevating shaft 23 passing,with a play, through the bottom of processing container 11 to be freelymovable upward and downward. Further, mounting table 22 is connected toa biasing high frequency power supply 26 through a matching box 25.Output frequency of high frequency power supply 26 is about severalhundred kHz to ten and several MHz. In order to ensure air-tightness ofprocessing container 11, a bellows 24 is provided to surround elevatingshaft 23, between mounting table 22 and insulating plate 14.

Above dielectric plate 12, a patch antenna 3030 is arranged forsupplying an electromagnetic field of a high frequency wave intoprocessing container 11 through dielectric plate 12. Patch antenna 3030is separated from processing container 11 by dielectric plate 12, andprotected from the plasma generated in processing container 11. Further,a shield member 18 covers peripheries of dielectric plate 12 and patchantenna 3030 to prevent leakage of the high frequency wave to theoutside of the etching apparatus.

Coaxial line 3041 is used for feeding patch antenna 3030. Coaxial line3041 is connected to feeding high frequency power supply 45 throughmatching box 3044. Output frequency of high frequency power supply 45 isapproximately 100 MHz-8 GHz. By providing matching box 3044 forimpedance matching, efficiency of power use can be improved.

FIGS. 22A and 22B show a configuration of patch antenna 3030 shown inFIG. 21. Here, FIG. 22A is a perspective view of patch antenna 3030,while FIG. 22B shows coordinate systems.

Patch antenna 3030 is a monopole patch antenna, and as shown in FIG.22A, it includes a ground plane 3031 formed of a grounded conductiveplate, a conductive plate 3032 having a quadrangular two-dimensionalshape for forming a resonator, and a conductive member 3033 connectingone end 3032A of conductive plate 3032 to ground plane 3031.

For ease of description, orthogonal coordinate systems are defined asfollows. y axis is set to be parallel to one end 3032A of conductiveplate 3032, x axis is set to be parallel to the other end that isadjacent to one end 3032A, and z axis is set in a direction leading fromground plane 3031 toward conductive plate 3032.

Conductive plate 3032 forming a resonator is quadrangular as describedabove. When the wavelength of the electromagnetic field in patch antenna3030 is given as λg, then the length of conductive plate 3032 in x axisdirection is set to approximately λg/4. Further, the length ofconductive plate 3032 in y axis direction is preferably less than λg/2.Conductive plate 3032 is arranged facing to and parallel to ground plane3031.

Conductive member 3033 connecting end 3032A of conductive plate 3032 toground plane 3031 is a plate-like member provided perpendicular toground plane 3031. The length of conductive member 3033 in y axisdirection is equal to that of conductive plate 3032, and its length in zaxis direction (i.e., height) is desirably 5-50 mm, approximately.

End 3032A of conductive plate 3032 is short-circuited to ground plane3031 by conductive member 3033, and therefore the potential of end 3032Ais fixed to 0 (zero). Hence, end 3032A is referred to as fixed end3032A. On the other hand, end 3032B facing to fixed end 3032A is open,and hence it is referred to as open end 3032B.

Ground plane 3031, conductive plate 3032 and conductive member 3033 areformed of copper, aluminum or the like. Patch antenna 3030 with such aconfiguration is arranged such that conductive plate 3032 is located atthe bottom facing to dielectric plate 12, as shown in FIG. 21.

As described above, coaxial line 3041 is used for feeding patch antenna3030. As shown in FIG. 21, outer conductor 3042 of coaxial line 3041 isconnected to ground plane 3031, while inner conductor (feed line) 3043of coaxial line 3041 penetrates an opening of ground plane 3031 to beconnected to conductive plate 3032 at feeding point P thereon. Whilefeeding point P is provided at a point away from end 3032A of conductiveplate 3032, it is desirable to be set in the vicinity of the center ofconductive plate 3032, as shown in FIG. 22A, considering impedancematching and the like.

Next, the principle of radiation of electromagnetic wave by patchantenna 3030 is described. FIGS. 23A and 23B are illustrations therefor.FIG. 23A shows conductive plate 3032, while FIG. 23B shows the voltagedistribution in x axis direction in conductive plate 3032.

The potential of fixed end 3032A of conductive plate 3032 is fixed to 0(zero), and that the length of conductive plate 3032 in x axis directionis λg/4. Therefore, the current supplied from high frequency powersupply 45 to conductive plate 3032 behaves as if the length ofconductive plate 3032 in x axis direction is λg/2, oscillating in x axisdirection to be a standing wave. Here, the voltage waveform repeats thechange shown in FIG. 23B.

When the voltage at open end 3032B of conductive plate 3032 is positive,the line of electric force is directed from conductive plate 3032 towardground plane 3031, and when the voltage at open end 3032B of conductiveplate 3032 is negative, the line of electric force is directed fromground plane 3031 toward conductive plate 3032. The direction of theline of electric force is the same as the direction of the displacementcurrent, and therefore a magnetic current is generated parallel to yaxis as shown in FIG. 23A. With this magnetic current as a wave source,a high frequency wave is emitted from patch antenna 3030 in z axisdirection.

Patch antenna 3030 has an excellent radiation efficiency of theelectromagnetic field, since its magnetic current forming portion (i.e.,the length of conductive plate 3032 in y axis direction) is longer ascompared to conventional dipole antenna 530. From the view point of theradiation efficiency, the length of conductive plate 3032 in y axisdirection should be longer. In order to decrease the effect of themagnetic current formed in the side face of patch antenna 3030 parallelto x axis, the length of conductive plate 3032 in y axis direction ispreferably set to at least λg/8, approximately.

Next, an operation of the etching apparatus shown in FIG. 21 will bedescribed.

The inside of processing container 11 is evacuated, for example, to adegree of vacuum of about 0.01-10 Pa, with substrate 21 placed on theupper surface of mounting table 22. While maintaining the degree ofvacuum, Ar as the plasma gas is supplied from plasma gas supply nozzle16, and CF₄ as the etching gas is supplied from processing gas supplynozzle 17, with the flow rate thereof being controlled.

When patch antenna 3030 is fed in the state where the plasma gas andetching gas is supplied into processing container 11, a high frequencywave is emitted from patch antenna 3030, as described above. Since patchantenna 3030 is shielded by ground plane 3031 in the upper direction,and by a shield member 18 in lateral directions, the high frequency wavepasses through dielectric plate 12 and introduced into processingcontainer 11. By forming the electric field in processing container 11to cause electrolytic dissociation of Ar, plasma is generated in anupper space A above substrate 21 to be processed. The plasma diffuses inprocessing container 11, and the energy, anisotropy or the like thereofis controlled by the bias voltage applied to mounting table 22 to beused in the etching process.

Patch antenna 3030 used in this etching apparatus is a monopole antenna,and as compared to conventional dipole antenna 530, the size of theantenna can be reduced. When forming conductive plate 3032 to be aresonator by, for example, λg/4 angle, a processing container having adiameter L of approximately λg/4-λg/2 or a high frequency wave having afrequency of approximately c/(4 L)-c/(2 L), which cannot be usedconventionally, can be utilized. Thus, the degree of freedom-indesigning the etching apparatus that has been limited by the antennasize can be increased.

Though conductive plate 3032 of patch antenna 3030 shown in FIG. 22A isillustrated as quadrangular two-dimensionally, it is only required tohave a substantially straight fixed end 3032A, and a length ofapproximately λg/4 in a direction perpendicular to fixed end 3032A (xaxis direction). As used herein, substantially straight means a conceptincluding not only a straight line but also a gentle curve. When fixedend 3032A is a gentle curve, open end 3032B opposing to fixed end 3032Amay be a shape on which fixed end 3032A overlaps when translated.Additionally, conductive plate 3032 may be trapezoid or semi-circletwo-dimensionally.

As shown in FIG. 24, a dielectric plate 3035 may be arranged betweenground plane 3031 and conductive plate 3032 forming patch antenna 3030A.Thus, the wavelength λg of the electromagnetic field on conductive plate3032 becomes shorter, which enables the patch antenna to be furthersmaller.

Seventh Embodiment

Next, a variation of patch antenna 3030 shown in FIG. 21 will bedescribed. FIGS. 25A and 25B show a configuration of the variation. FIG.25A is a perspective view, while FIG. 25B shows coordinate systems. Inthese figures, portions similar to those in FIGS. 22A and 22B aredenoted by similar reference characters, and description thereof willappropriately be omitted.

Patch antenna 3130 shown in FIG. 25A has, in the configuration of patchantenna 3030 shown in FIG. 21, open end 3032B of conductive plate 3032folded toward ground plane 3031, and conductive member 3031 partiallycut out to be a narrow shape.

In the following, description will be made in detail. In patch antenna3130, the length of conductive plate 3132 forming a resonator in x axisdirection is at least approximately λg/8 and less than approximatelyλg/4.

Additionally, to conductive plate 3132, a conductive plate 3134extending from open end 3132B toward ground plane 3031 is connected. Thelength of conductive plate 3134 in y axis direction is the same as thatof conductive plate 3132, while the length thereof in z axis directionis shorter than that of conductive member 3133. Accordingly, the tip ofconductive plate 3134 does not contact ground plane 3031. Further,conductive plate 3134 is made of the same material as conductive plate3132 and the like, i.e., copper or aluminum.

Still further, conductive member 3133 connecting fixed end 3132A ofconductive plate 3132 to ground plane is shorter in y axis directionthan conductive plate 3132.

When patch antenna 3130 with such a configuration is fed, largecapacitance is formed between conductive plate 3134 and ground plane3031. Additionally, large inductance is formed in the narrow conductivemember 3133. By designing the apparatus such that these capacitance andinductance compensate each other, the length of conductive plate 3132 inx axis direction can be shortened to approximately λg/8.

Though patch antenna 3130 is smaller than patch antenna 3030 shown inFIG. 21, it can emit a high frequency wave equivalent to those emittedby patch antenna 3030.

In patch antenna 3130 also, the patch antenna can be made furthersmaller by arranging dielectric plate 3035 as shown in FIG. 24 betweenground plane 3031 and conductive plate 3132.

In the foregoing, while the example has been described where the plasmaapparatus according to the third invention is applied to an etchingapparatus, it is needless to say that it may be applied to other plasmaapparatus such as a plasma CVD apparatus.

As described above, according to the plasma apparatus of the thirdinvention, by forming the antenna supplying the high frequencyelectromagnetic field into the processing container by a monopoleantenna to make the antenna smaller, the degree of freedom in designingthe plasma apparatus can be increased, which has been limited by thesize of the antenna.

Further, by using the patch antenna as the monopole antenna, theradiation efficiency of the high frequency wave can be improved.

In the following, referring to the figures, embodiments according to afourth invention of the present invention will be described in detail.Here, an example will be described where a plasma apparatus according tothe fourth invention is applied to an etching apparatus.

Eighth Embodiment

FIG. 26 shows a configuration of an etching apparatus according to aneighth embodiment of the present invention. FIG. 26 shows a crosssection of a partial configuration thereof.

The etching apparatus shown in FIG. 26 has a cylindrical processingcontainer 11 that is open at an upper portion. Processing container 11is formed of a conductive member such as aluminum.

At the upper opening of processing container 11, a dielectric plate 12formed of quartz glass or ceramic (such as Al₂O₃ or AlN) having athickness of about 20-30 mm is arranged. At a joint portion betweenprocessing container 11 and dielectric plate 12, a sealing member 13such as an O-ring is interposed, to ensure air-tightness insideprocessing container 11.

At the bottom of processing container 11, an insulating plate 14 formedof ceramic or the like is provided. Further, an exhaust port 15 isprovided penetrating through insulating plate 14 and the bottom ofprocessing container 11 and, by means of a vacuum pump (not shown)communicated with exhaust port 15, the inside of processing container 11can be evacuated to a desired degree of vacuum.

At upper portion and lower portion of a sidewall of processing container11, a plasma gas supply nozzle 16 is provided for introducing a plasmagas such as Ar and a processing gas supply nozzle 17 is provided forintroducing an etching gas into processing container 11, respectively.Plasma gas supply nozzle 16 and processing gas supply nozzle 17 areformed by a quartz pipe or the like.

In processing container 11, a mounting table 22 is contained, on anmounting surface of which a substrate 21 to be etched (the object to beprocessed) is placed. Mounting table 22 is supported by an elevatingshaft 23 passing, with a play, through the bottom of processingcontainer 11 to be freely movable upward and downward. Further, mountingtable 22 is connected to a biasing high frequency power supply 26through a matching box 25. Output frequency of high frequency powersupply 26 is a prescribed frequency within the range of several hundredkHz to ten and several MHz. In order to ensure air-tightness ofprocessing container 11, a bellows 24 is provided to surround elevatingshaft 23, between mounting table 22 and insulating plate 14.

Above dielectric plate 12, a patch antenna 4030 is arranged forsupplying a high frequency electromagnetic field into processingcontainer 11 through dielectric plate 12. Patch antenna 4030 isseparated from processing container 11 by dielectric plate 12, andprotected from the plasma generated in processing container 11. Further,a shield member 18 covers peripheries of dielectric plate 12 and patchantenna 4030 to prevent leakage of the high frequency electromagneticfield from patch antenna 4030 to the outside of the etching apparatus.

Patch antenna 4030 has ground plane 4031 formed of a grounded conductiveplate, and a conductive plate 4032 forming a resonator (hereinafterreferred to as a patch). Patch 4032 is arranged facing to ground plane4031 with a prescribed distance, and the distance is maintained by ashort pin 4033 connecting respective center. Ground plane 4031, patch4032 and short pin 4033 are formed of copper, aluminum or the like.Patch antenna 4030 is arranged such that patch 4032 is located at thebottom facing to the mounting surface of mounting table 22 anddielectric plate 12.

Patch antenna 4030 is fed at two points. Two coaxial lines (firstfeeding lines) 4041A and 4041B are employed for the feeding. It is notedthat coaxial line 4041B is longer in electrical length than coaxial line4041A by 180°. As used herein, the electrical length is expressed by thephase difference when feeding electricity passes through coaxial lines4041A, 4041B. In this case, it means that their feeding phases to patchantenna 4030 are different by 180°.

Coaxial lines 4041A and 4041B are connected to feeding high frequencypower supply 45 through matching boxes 4044A and 4044B, respectively.Output frequency of high frequency power supply 45 is a prescribedfrequency in a range of 100 MHz-8 GHz. Additionally, by interposingmatching boxes 4044A and 4044B for improving impedance matching tocoaxial lines 4041A and 4041B, respectively, the efficiency of power usecan be improved.

FIG. 27A is a plan view of patch 4032 in FIG. 26 viewed from the bottom.As shown in FIG. 27A, patch 4032 has a two-dimensional shape of a squarein which the length L of one edge is approximately 3×λg/2. λg is awavelength of the electromagnetic field between patch 4032 and groundplane 4031, of which value is determined by the permittivity betweenpatch 4032 and ground plane 4031. Here, it is assumed that center O ofpatch 4032 is located at the origin of coordinate systems, while eachedge of patch 4032 is parallel to x axis and y axis.

In this case, two feeding points P, Q of patch 4032 are provided at twopoints away from center O in the opposite directions by approximatelyλg/4 on x axis (first line). As shown in FIG. 26, as described above,feeding points P, Q are connected to inner conductors 4043A and 4043B ofcoaxial lines 4041A and 4041B, respectively, with coaxial line 4041Bconnected to feeding point Q being longer than coaxial line 4041Aconnected to feeding point B by 180°. It is noted that outer conductors4042A and 4042B of coaxial lines 4041A and 4041B are connected to groundplane 4031.

Here, referring to FIGS. 27A-27C, the operating principle of patchantenna 4030 is described.

Two coaxial lines 4041A and 4041B are connected on x axis of patch 4032,with the length of patch 4032 in x axis direction being approximately3×λg/2. Thus, the current supplied from two coaxial lines 4041A and4041B resonates in x axis direction to be a standing wave. Here, byfeeding at two feeding points P, Q, the mode of the standing wave isdefined. The voltage waveform in x direction is as shown in FIG. 27B,with the opposing ends becoming antinodes and the number of waves being3/2. Hence, the voltage variations at opposing ends show oppositephases. Accordingly, as shown in FIG. 27A, along opposing sides of patch4032 in x axis direction, i.e., along two edges parallel to y axis,magnetic currents are generated in reverse directions as viewed from thecenter of patch 4032. Specifically, when one of the magnetic current isdirected to the positive direction (or the negative direction) of yaxis, the other magnetic current is also directed to the positivedirection (or the negative direction) of y axis. Accordingly, in patchantenna 4030, only TM11 mode is excited, and TM01 mode is not excited.It is noted that high frequency wave is emitted having two magneticcurrents as the wave source.

Next, an operation of the etching apparatus shown in FIG. 26 will bedescribed.

The inside of processing container 11 is evacuated, for example, to adegree of vacuum of about 0.01-10 Pa, with substrate 21 placed on themounting surface of mounting table 22. While maintaining the degree ofvacuum, Ar as the plasma gas is supplied from plasma gas supply nozzle16, and CF₄ as the etching gas is supplied from processing gas supplynozzle 17, with the flow rate thereof being controlled.

In the state where the plasma gas and the etching gas are supplied intoprocessing container 11, patch antenna 4030 is fed at two feeding pointsP, Q in the same amplitude and with phases different by 180° from eachother. Thus, patch antenna 4030 is selectively excited to TM11 mode. InTM11 mode, the directivity of high frequency electromagnetic field willbe z axis direction perpendicular to the main surface (xy plane) ofpatch 4032, therefore the electromagnetic field is oriented directlytoward substrate 21 to be etched.

The electric field causes electrolytic dissociation of Ar in processingcontainer 11 to generate plasma in an upper space 50 above substrate 21to be processed. The plasma diffuses in processing container 11, and theenergy, anisotropy or the like thereof is controlled by the bias voltageapplied to mounting table 22 to be used in the etching process.

As described above, in this etching apparatus, the electromagnetic fieldis oriented directly toward substrate 21, therefore the power that isconverted to thermal energy at shield member 18 or processing container11 before contributing to plasma generation is decreased as compared tothe conventional etching apparatus shown in FIG. 41. Thus, the powercontributing to the plasma generation is increased. Accordingly, theefficiency of power at the plasma generation can be increased ascompared to the conventional manner.

In FIG. 27A, it has been described that two feeding points P, Q are on xaxis of patch 4032. This prevents the current from passing through yaxis direction on patch 4032, which will suppress the radiation of ahigh frequency wave from two edges of patch 4032 parallel to x axis.Nevertheless, feeding points P, Q can be provided at points offset fromx axis in a range in which the effect of the radiation can be permitted.

Additionally, though it has been described that two feeding points P, Qare provided away from center O on patch 4032 by the same distance, theymay be provided at positions away from center O by different distances.However, since the potential will be 0 (zero) at the positionscorresponding to nodes of a standing wave, it is not desirable toprovide feeding points P, Q to such a position or in the vicinitythereof. Accordingly, it is desirable to provide feeding points P, Q atpositions away from positions corresponding to the nodes of a standingwave by at least λg/16.

Further, since it is only required to define the mode of a standing wavegenerated in patch 4032 by two-point feeding, the distance d between twofeeding points P, Q is not necessarily λg/2 and the feeding phasedifference be 180°. Additionally, they are not necessarily correlatedwith each other. However, taking into account of the relationshipbetween the nodes of the standing wave and feeding points P, Q asdescribed above, the desirable minimum value of distance d betweenfeeding points P, Q is approximately λg/8.

Still further, the length L of one edge of patch 4032 of patch antenna4030 may be approximately (N+½)×λg (N is an integer at least 0).

Still further, two-dimensional shape of patch 4032 may be a quadrangleother than a square. In this case, when the length in x axis directionis L1≈(N+½)×λg, the length in y axis direction may be{(N′−1)+½}×λg<L2<(N′+½)×λg (N′ is an integer of 0≦N′≦N).

Still further, two-dimensional shape of the patch may be a circle aspatch 4132 shown in FIG. 28. In this case, the diameter L of the circlemay be approximately 1.17×(N+½)×λg. This dimension is a concept includedin the approximate (N+½)×λg as described above. L≈1.8×λg shown in FIG.28 is an example where N=1.

As shown in FIG. 29, a dielectric plate 4034 formed of ceramic or thelike may be interposed between ground plane 4031 and patch 4032 formingpatch antenna 4030. Thus, the patch antenna can be made smaller. In thiscase, short pin 4033 connecting patch 4032 and ground plane 4031 may notnecessarily provided.

Still further, though FIG. 27A illustrates to provide two feeding pointsP, Q on x axis of patch 4032, feeding points may be provided two each(P1, Q1), (P2, Q2) on at least two lines (first lines) x1, x2 that areperpendicular to the outer periphery of patch 4032 as shown in FIG. 30.The matching box is omitted from FIG. 30.

Ninth Embodiment

FIG. 31 shows a configuration for generating a circular polarizationusing patch antenna 4030 shown in FIG. 26. In this figure, portionssimilar to those of FIGS. 26, 27A-27C are denoted by the same referencecharacters, and description thereof will appropriately be omitted.

When generating a circular polarization, two additional feeding pointsR, S are provided on patch 4032 forming a resonator. These feedingpoints R, S are provided on y axis (second line) at two points away fromcenter O by approximately λg/4 in opposite directions.

Inner conductors 4043C and 4043D of coaxial lines (second feeding lines)4041C and 4041D are connected to feeding points R, S, with coaxial line4041D connected to feeding point S being longer in electrical lengththan coaxial line 4041C connected to feeding point R by 180°.Additionally, coaxial lines 4041C and 4041D are longer in electricallength than coaxial lines 4041A and 4041B by 90°, respectively.Accordingly, the feeding point phase difference for feeding points R, Sis 180°, and feeding points R, S are fed with phases lagging fromfeeding points P, Q by 90°, respectively. It is noted that matchingboxes 4044C and 4044D are interposed in coaxial lines 4041C and 4041D,respectively.

FIGS. 32A-32C illustrate the operating principle of patch antenna 4030with four-point feeding as shown in FIG. 31, FIG. 32A shows a magneticcurrent generated around patch 4032, FIG. 31B shows the voltage waveformon x axis, and FIG. 31C shows the voltage waveform on y axis.

When patch 4032 is fed at two feeding points P, Q on x axis thereof withequal amplitude, then a high frequency wave is emitted having twomagnetic currents parallel to y axis as the wave source, in the sameprinciple described above with reference to FIGS. 27A-27C. This highfrequency wave will be a linear polarization parallel to x axis.Similarly, when patch 4032 is fed at two feeding points R, S on y axisthereof with equal amplitude, then the high frequency wave is emittedhaving two magnetic currents parallel to x axis as the wave source. Thehigh frequency wave will be a linear polarization parallel to y axis. Atthis time, feeding points Q, R are fed with phases lagging from feedingpoints P, Q by 90°, respectively, and therefore the phase of the linearpolarization parallel to y axis lags by 90° from that of linearpolarization parallel to x axis. These two linear polarizations haveequal amplitude, perpendicular spatially, and out of phase by 90° toeach other, and therefore they form a circular polarization. In thiscase, it will be a right-hand circular polarization in the verticaldirection in FIG. 26 (positive direction in z axis).

When two-point feeding is employed as shown in FIGS. 26 and 27A, as thehigh frequency wave emitted by patch antenna 4030 will be a linearpolarization parallel to x axis, the electric field distribution thereofwill be as shown in FIGS. 33A and 33B. Specifically, though it isrelatively uniform on xz plane as shown in FIG. 33A, it is biased on yzplane as shown in FIG. 33B.

Though bias is still present on the electric field distribution in thelinear polarization parallel to x axis or y axis itself when four-pointfeeding is employed as shown in FIG. 31, by generating the circularpolarization to rotate the electromagnetic field around the axisperpendicular to the mounting surface of mounting table 22, the plasmadistribution generated by the electromagnetic field rotates as well.Thus, the etching process that is uniform when averaged by time can beattained.

It is noted that, when employing four-point feeding to generate thecircular polarization, the two-dimensional shape of patch 4032 may be90° rotationally symmetrical shape such as a square or a circle (a shapethat overlaps when rotated by 90° around the central axis of patch4032), or may be a shape having different lengths in two directionsperpendicular to each other viewed from center O, such as a rectangle.In the case of the latter, the feeding phase difference of feedingpoints P, R and feeding points Q, S may not be set 90°, and it may beadjusted by the lengths of the two directions. In either case of theformer and the latter, the two perpendicular lengths are required to beapproximately (N+½)×λg, and approximately (M+½)×λg (N, M are integers atleast 0).

Further, in the four-point feeding scheme shown in FIG. 31, it has beendescribed that the right-hand circular polarization is emitted in thevertical direction of FIG. 26 (positive direction of z axis). To emitthe left-hand circular polarization, coaxial lines 4041C and 4041D maybe set to have electrical lengths longer than coaxial lines 4041A and4041B by 90°, respectively.

Still further, the high frequency wave emitted by the patch antenna 4030is not necessarily a perfectly circular polarization. Given that thepolarization ratio of a circular polarization of which length of longaxis is 2a and that of short axis is 2 b as shown in FIG. 34 is b/a(×100)%, generation of the circular polarization with a polarizationratio of at least 50%, preferably at least 70% results in theimprovement of the plasma distribution.

Here, a method for adjusting the polarization ratio of a circularpolarization is described briefly.

First, when two linear polarizations perpendicular to each other are outof phase to each other by 90° but with different amplitude values, giventhat the two linear polarizations are expressed as a sin (ωt+π/2), b sin(ωt), then the polarization ratio is simply determined by the amplitudevalue ratio b/a (×100)%. Therefore, in order to obtain the polarizationratio of at least 70%, the amplitude value ratio may only be set to atleast 70%.

Additionally, when two linear polarizations perpendicular to each otherare equal in amplitude value but with a phase difference other than 90°,given that the two linear polarizations are expressed as sin (ωt−θ),sin(ωt), then the phase difference dependency of the polarization ratiowhen the phase difference 0 takes on the value in the vicinity of 90°will be as shown in FIG. 35. Therefore, in order to obtain thepolarization ratio of at least 70%, the phase difference 0 may only beadjusted to approximately 70°-110°.

Further, when feeding-points are provided two each (P1, Q1), (P2, Q2) ontwo lines x1, x2 as shown in FIG. 30, feeding points are provided twoeach (R1, S1), (R2, S2) on two lines y1, y2 perpendicular to lines x1,x2, respectively, as in patch 4132 shown in FIG. 36. Then, feeding maybe carried out such that the feeding phase differences between feedingpoints P1 and R1, feeding points Q1 and S1, feeding points P2 and R2, aswell as feeding points Q2 and S2 are about the same.

In the foregoing, while the example has been described where the plasmaapparatus according to the fourth invention is applied to an etchingapparatus, it is needless to say that it may be applied to other plasmaapparatus such as a plasma CVD apparatus.

As described above, in the plasma apparatus according to the fourthinvention, the antenna is fed at two points to selectively excite theTM11 mode. Thus, the high frequency wave will be oriented directly tothe object to be processed, which results in reduction of the powerabsorbed by the processing container or the like to increase the powerthat contributes in plasma generation. Hence, the efficiency of power inplasma generation can be improved.

Still further, by making the high frequency wave supplied from theantenna into the processing apparatus to the circular polarization, torotate the electromagnetic field around the axis perpendicular to themounting surface of mounting table, the plasma distribution generated bythe electromagnetic field rotates as well. Thus, the uniformity ofplasma distribution when averaged by time can be improved.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the spiritand scope of the present invention being limited only by the terms ofthe appended claims.

INDUSTRIAL APPLICABILITY

The present invention may be applied to a plasma apparatus for processessuch as oxide film formation, crystal growth of a semiconductor layer,etching and ashing, in manufacturing semiconductor devices. Accordingly,it can contribute to improving the semiconductor apparatus manufacturingtechnology.

1. A plasma apparatus, comprising: a mounting table arranged in anair-tight processing container for mounting an object to be processed;and an antenna arranged facing to said mounting table for supplying ahigh frequency wave into said processing container; wherein said antennahas a conductive plate (1032) arranged facing to said mounting table toform a resonator, and a ground plane (1031) arranged facing to saidconductive plate at a side opposite to said mounting table, and saidconductive plate is fed such that said high frequency wave becomes acircular polarization.
 2. The plasma apparatus according to claim 1,wherein said conductive plate is fed such that said high frequency wavebecomes a circular polarization having a polarization ratio of at least50%.
 3. The plasma apparatus according to claim 1, further comprisingtwo feeding lines feeding said conductive plate.
 4. The plasma apparatusaccording to claim 3, wherein said two feeding lines feed such that twolinear polarizations equal in amplitude, having different phases fromeach other by 90°, and spatially perpendicular to each other areemitted, respectively.
 5. The plasma apparatus according to claim 4,wherein said conductive plate has a two-dimensional shape of a 90°rotationally symmetrical shape, and said two feeding lines are connectedto said conductive plate at two points thereon away from a center ofsaid conductive plate by substantially equal distances and in twodirections perpendicular to each other as viewed from said center, forfeeding in equal amplitude and with phases different from each other by90°, respectively.
 6. The plasma apparatus according to claim 1, whereinsaid conductive plate has a two-dimensional shape with two differentlengths in two directions perpendicular to each other as viewed fromsaid center, said plasma apparatus further comprising a feeding lineconnected to said conductive plate at one point thereon in a directionbetween said two directions, for feeding said conductive plate.
 7. Theplasma apparatus according to claim 6, wherein said conductive plate hasa two-dimensional shape of a circle of which peripheral region is cutout partially.
 8. The plasma apparatus according to claim 6, whereinsaid conductive plate has a two-dimensional shape of an ellipse or aquadrangle.
 9. A plasma apparatus, comprising: a mounting table arrangedin an air-tight processing container and having a mounting surface formounting an object to be processed; and an antenna arranged facing tosaid mounting surface of said mounting table for supplying anelectromagnetic field of a high frequency wave into said processingcontainer; wherein said antenna is formed of a plurality of monopoleantennas, and configured such that said electromagnetic field forms acircular polarization.
 10. The plasma apparatus according to claim 9,wherein said electromagnetic field emitted by said antenna has apolarization ratio of at least 50%.
 11. A plasma apparatus, comprising:a mounting table arranged in an air-tight processing container andhaving a mounting surface for mounting an object to be processed; and anantenna arranged facing to said mounting surface of said mounting tablefor supplying an electromagnetic field of a high frequency wave intosaid processing container; wherein said antenna is formed of a pluralityof monopole antennas, and configured such that said electromagneticfield forms a substantial TM01 mode.
 12. The plasma apparatus accordingto claim 9, wherein each of said plurality of monopole antennas is apatch antenna.
 13. The plasma apparatus according to claim 12, whereinsaid patch antenna includes a conductive plate arranged facing to saidmounting surface of said mounting table, a ground plane arranged facingto said conductive plate at a side opposite to said mounting table asviewed from said conductive plate, a conductive member connecting oneend of said conductive plate to said ground plane, and a feeding lineconnected to said conductive plate at a point away from said one end ofsaid conductive plate, wherein said one end of said conductive plate ofsaid patch antenna is substantially straight, and a length in adirection perpendicular to said one end is at most approximately ¼ of awavelength of the electromagnetic field in said patch antenna.
 14. Theplasma apparatus according to claim 13, wherein said conductive plate ofsaid patch antenna has other end opposing to said one end folded towardsaid ground plane, said one end being connected to said conductivemember, and said conductive member of said patch antenna has one lengthin a same direction as said one end of said conductive plate formedshorter than said one end.
 15. The plasma apparatus according to claim12, wherein said patch antenna including a conductive plate arrangedfacing to said mounting surface of said mounting table and havingsubstantially straight one end and arc-shaped other end opposing to saidone end, a length between said one end and said other end being at most(1.17±0.05)/4 of a wavelength of said electromagnetic field in saidpatch antenna, a ground plane arranged facing to said conductive plateat a side opposite to said mounting table as viewed from said conductiveplate, a conductive member connecting said one end of said conductiveplate to said ground plane, and a feeding line connected to saidconductive plate at a point away from said one end of said conductiveplate.
 16. The plasma apparatus according to 15, wherein said conductiveplate of said patch antenna has said other end folded toward said groundplane, and said conductive member of said patch antenna has one lengthin a same direction as said one end of said conductive plate formedshorter than said one end.
 17. A plasma apparatus, comprising: amounting table arranged in an air-tight processing container formounting an object to be processed; and an antenna arranged facing tosaid mounting table for supplying an electromagnetic field of a highfrequency wave into said processing container; wherein said antenna is amonopole antenna.
 18. The plasma apparatus according to claim 17,wherein said monopole antenna is a patch antenna.
 19. The plasmaapparatus according to claim 18, wherein said patch antenna including aconductive plate arranged facing to said mounting table and havingsubstantially straight one end, a length of said conductive plate in adirection perpendicular to said one end being at most approximately ¼ ofa wavelength of said electromagnetic field in said patch antenna, aground plane (3031) arranged facing to said conductive plate at a sideopposite to said mounting table as viewed from said conductive plate, aconductive member connecting said one end of said conductive plate tosaid ground plane, and a feeding line connected to said conductive plateat a point away from said one end of said conductive plate.
 20. Theplasma apparatus according to claim 19, wherein said conductive plate ofsaid patch antenna has other end (3132B) facing to said one endconnected to said conductive member folded toward said ground plane, andsaid conductive member of said patch antenna has one length in a samedirection as said one end of said conductive plate formed shorter thansaid one end.
 21. The plasma apparatus according to claim 19, furthercomprising a dielectric plate arranged between said conductive plate andsaid ground plane.
 22. A plasma apparatus, comprising: a mounting tablearranged in an air-tight processing container for mounting an object tobe processed; and an antenna arranged facing to said mounting table forsupplying a high frequency wave into said processing container; whereinsaid antenna includes a conductive plate arranged facing to saidmounting table, a ground plane arranged facing to said conductive plateat a side opposite to said mounting table as viewed from said conductiveplate, and a plurality of first feeding lines connected to saidconductive plate, wherein two each of said first feeding lines areconnected away from each other to at least one first line on saidconductive plate perpendicular to a periphery of said conductive plate,and each of said first feeding lines has a length of approximately(N+½)×λg (N is an integer at least 0), where λg is a wavelength of anelectromagnetic field between said conductive plate and said groundplane.
 23. The plasma apparatus according to claim 22, wherein saidfirst line passes through a center of said conductive plate.
 24. Theplasma apparatus according to claim 22, wherein said antenna furtherincluding includes a plurality of second feeding lines connected to saidconductive plate, two each of said second feeding lines being connectedaway from each other to at least one second line on said conductiveplate perpendicular to corresponding said first line, wherein each ofsaid second lines has a length of approximately (M+½)×λg (M is aninteger at least 0), each of said second feeding lines feeds with a samedegree of phase lag behind corresponding said first feeding lines, suchthat said high frequency wave becomes a circular polarization.
 25. Theplasma apparatus according to claim 24, wherein each of said secondfeeding lines feeds such that said high frequency wave becomes acircular polarization having a polarization ratio of at least 50%. 26.The plasma apparatus according to claim 24, wherein said first andsecond lines pass through a center of said conductive plate.
 27. Theplasma apparatus according to claim 22, wherein a distance between saidtwo first feeding lines connected to the same first line is λg/2. 28.The plasma apparatus according to claim 24, wherein a distance betweensaid two first feeding lines connected to the same first line, and adistance between said two second feeding lines connected to the samesecond line are each λg/2.